1. Field of the Invention
This invention relates generally to a system of toothed belt and sprocket profiles having a tooth flank engaging a predetermined portion of the sprocket groove such that the land pressure is reduced, and more particularly to a belt having a truncated tooth tip forming a reservoir between tooth and sprocket groove, and with the tooth engaging a predetermined portion of the sprocket groove such that the tooth is supported by an interference fit in a manner to reduce land pressure.
The prior art belt and sprocket system is based on a mold groove profile with clearance between a belt tooth tip and the bottom of the pulley groove. There is also some shrinkage in the belt tooth height after curing that increases this clearance between the belt tooth tip and pulley groove bottom. This clearance can cause the pitch line of the belt to become chordal over the pulley groove as the belt teeth in rack form mesh with the sprocket grooves. The chordal action causes undue wear in the land portion of the belt. The forces within the belt must be supported by the pulley. This support consists of pressures that develop and are distributed between the tooth tip/groove bottom, the tooth flank/pulley flank, and the belt land between the belt teeth. The portion of this support distributed on the belt land can be large enough to result in undue wear of the land portion of the belt.
Further, as the belt pitch line is repeatedly raised and lowered by the driver and driven sprocket teeth through chordal action, the angular velocity of the driven sprocket alternately increases and decreases. This cogging action can be felt as a vibration in the system.
2. Description of the Prior Art
A number of design strategies for toothed belt and pulley profiles have been proposed in the prior art. Representative of the art is U.S. Pub No 2009/0156341 which discloses a belt and sprocket system comprising a tensile cord disposed within a belt body, a tooth projecting from the belt body, the tooth having a profile having at least two unequal radii connected in series and disposed between a tooth tip and a tooth root, a sprocket having a groove for receiving the tooth, the groove profile comprising at least one substantially linear portion disposed between the at least two unequal radii, a tooth tip engaging a predetermined portion of the sprocket groove such that the tensile cord is supported in a manner to cause the tensile cord to have a substantially arcuate form between the tooth roots.
What is needed is a belt having a truncated tooth tip forming a reservoir between tooth and sprocket groove, and with the tooth engaging a predetermined portion of the sprocket groove such that the tooth is supported by an interference fit in a manner to reduce land pressure. The present invention meets this need.